The present invention relates generally to loopback testing of field replaceable units in a system with a host adapter and at least one other device connected together. More particularly, the invention is directed at testing devices in a daisy chain configuration to isolate malfunctions in such a system.
Problems in a system utilizing a cabling network are very difficult to isolate because cabling between devices and host adapters is very complex. In addition, in a daisy chain configuration, all of the devices are connected together and the numerous cables form, in essence, one cable. One method for determining the cause of a malfunction in a cabling network is to remove one device at a time. After removing a particular device, the system is tested to see if the problem has been eliminated. In some cases more than one device may be malfunctioning. This means that to determine which units are malfunctioning, each and every unit in the system may need to be removed. Using this method can be both frustrating and time consuming.
Another form of testing cables in a cable network is to examine each cable connection to make sure it is secure. In some cases if there is a loose pin inside a connector, moving or shaking the connector can make the difference between proper operation and malfunction. This technique is very unscientific and is a last resort for a user trying to locate a problem in the system. As with the previous technique, the user may become frustrated and may incur a needless waste of time.